Loans and Leases - Average recorded investment in impaired loans and leases and an analysis of interest on impaired loans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	$ 40,542	$ 42,908	$ 42,217	$ 42,590
Interest Income Recognized	184	112	376	175
Interest Income That Would Have Been Recognized Under Original Terms	413	512	876	1,070
Commercial, financial and agricultural [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	2,469	6,011	2,731	5,596
Interest Income Recognized	8	31	16	33
Interest Income That Would Have Been Recognized Under Original Terms	23	60	62	152
Real estate-commercial real estate [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	21,434	19,863	22,732	20,421
Interest Income Recognized	147	44	302	87
Interest Income That Would Have Been Recognized Under Original Terms	191	257	416	526
Real estate-construction [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	15,675	16,639	15,758	16,250
Interest Income Recognized	28	35	56	52
Interest Income That Would Have Been Recognized Under Original Terms	185	190	369	385
Real estate-residential secured for business purpose [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	169	161	178	140
Interest Income Recognized
Interest Income That Would Have Been Recognized Under Original Terms	2	2	5	3
Real estate-residential secured for personal purpose [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	751	185	773	130
Interest Income Recognized
Interest Income That Would Have Been Recognized Under Original Terms	12	3	24	4
Real estate-home equity secured for personal purpose [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	6		3	4
Interest Income Recognized
Interest Income That Would Have Been Recognized Under Original Terms
Loans to individuals [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	38	49	42	49
Interest Income Recognized	1	2	2	3
Interest Income That Would Have Been Recognized Under Original Terms